Driving a vehicle with correctly inflated tires can notably reduce fuel consumption and road safety risks. Indeed, under-inflated tires are more prone to stress damage, have less lateral traction, have a shorter tread life and are more vulnerable to flat fires and blow outs. Furthermore, under-inflated tires can increase the distance required for a vehicle to stop, especially if the surface is wet. In order to tackle this problem, several governments throughout the world have adopted mandatory standards for installing Tire Pressure Monitoring Systems (TPMS) in vehicles. In fact with a TPMS, the driver of a vehicle is notified when a tire is significantly under-inflated. TPMS are also essential to warn the driver in case of air pressure loss of so-called runflat tires, which are designed to be safely driven while uninflated or underinflated due to a puncture or the like. A direct TPMS is configured to measure the air pressure directly inside the tire. For this, the TPMS needs to be located in the tire, usually attached to the inflation valve of the tire. The TPMS then transmits a signal proportional to the pressure measurement e.g. via RF to a central receiver which is usually mounted under the dashboard of the vehicle. Finally, the central receiver in operation will receive the signal, decode it, analyse it and send the pressure information to the display (e.g. LCD display) viewable by the driver of the vehicle.
In certain implementations of direct TPMS, the link that exists between the TPMS and the central receiver is solely unidirectional. This may be problematic since foregoing TPMS standards prescribe that pressure information from a tire must be measured while the vehicle is in motion. Hence, in case of a unidirectional link, the TPMS cannot be informed about the vehicle being in motion for example by the central receiver. Consequently in such case, the TPMS has to determine by itself that the vehicle is in motion. This is why direct TPMS usually comprise an accelerator sensor in addition to the pressure sensor. In this configuration a TPMS developer, in addition to the program code needed to determine the tire pressure, must write a program code to determine motion by verifying the state of the accelerator sensor at different points in time. TPMS program code development is quite challenging due to the fact that every TPMS operation, such as tire pressure or acceleration determination, must have the lowest power consumption possible since direct TPMS have their own independent power source (e.g. a battery) that cannot be changed once the TPMS is installed in the tire. Therefore, in order to fulfill lifetime requirements, power-hungry operations of the TPMS need to be reduced when possible.